Water-soluble paper and method of making it



United States Patent 3,034,922 WATER-SOLUBLE PAPER AND METHOD OF MAKINGIT Hans Bile, Augsburg, Germany, assignor to Firms Carl Freudenberg,Kommanditgesellsehaft auf Aktien, Weinheim-Bergstr., Germany No Drawing.Filed July 23, 1959, Ser. No. 828,943

Claims priority, application Germany Aug. 1, 1953 2 Claims. (Cl. 117-63)The essential process in the manufacture of paper is the felting of thefibres, which are necessary for the formation of the paper, in theshaking screen machine, leading to the formation of a fibrous mass whichis no longer soluble in water. Paper, even when it is unsized, forexample filter or blotting paper, is therefore insoluble in water. It istrue that the paper fibres will swell and that the wet strength of thepaper is lower than the dry strength, but the fibre bond remains stable,so that any wet paper can be dried and its original strength thus moreor less restored.

If the paper is additionally sized, as for example with Writing paper,the material has great resistance to water and is stable and relativelyunchanged even after remaining in contact with water for hours.

A paper which disintegrates into its component parts in water cannottherefore be produced by the normal papermaking method, as the feltingof the paper fibres results in a bond which is stable even in water.

It has now been found that a paper which in water disintegrates into itsindividual components can be produced by impregnating with a suitablewater-soluble and film-forming substance fibres which have been unitedto form a loose fibre fleece, for example by means of carding machinesor fiat cards or by means of a Rando-Webb machine, thereupon drying themand forming the resulting material, if desired after re-wetting, into apaper-like product by calendering.

Natural and synthetic fibres, such as cotton, linen, hemp, ramie, Wool,viscose staple fibre, acetate staple fibre, Perlon, nylon, Trevira,polyvinyl alcohol fibres or alginate fibres, are suitable for thisprocess.

Water-soluble, film-forming substances may be used as binders, such asfor example methyl cellulose, cellulose glycolates, polyacrylic acid andacrylates, polymerisation products on a basis of vinyl pyrrolidone,polycarboxylic acids, water-soluble urea formaldehyde condensationproducts, decomposed glues, water-soluble starch products, dextrins, andsugars; alkali, ammonium, and triethanolamine alginates; carrageen mosssolutions, alkali caseinates, or waterglass (alkali metal silicate). Theamount of the water-soluble film-forming binder to be incorporated inthe fibrous structure is preferably 40%- 100% of the weight of thefibres.

Known fillers, such as kaolin, chalk, talcum, gypsum, magnesite, pearlwhite, lithopone, titanium dioxide, kieselguhr, microcellulose,asbestos, and if desired emollients or hygroscopic media, such asglycerine, glycols, polyglcols, and urea, and if desired water-solubledyestufis may be added to these binders and the loose fibre fleece maybe impregnated with an aqueous mixture on any of the well-knownmachines, e.g. a screen saturator, and dried. The concentration of saidaqueous mixture depends upon the type of the employed machine.Generally, the aqueous mixture should contain 5 to 50% of saidfilm-forming binders and fillers. Those skilled in the art will find outthe preferable concentration for a specific case without difiiculties.The amount of the fillers and emollients which may be added preferablyamounts to 60%-200% of the weight of the dry fibers. The resultingintermediate product, after first being wetted "icethe handle and thesmoothness of the finished material depends on the pressure and thetemperature of the rolls.

Thus it ispossible to produce papers, which in water disintegrate intotheir constituents. The weight of such paper is about 40 grams persquare metre for carbon copy paper, grams per square metre for writingpapers, and to grams per square metre for book papers or the like. Thesepapers can be written on normally with ink, ball point pen, or pencil,or used to make the normal number of carbon copies in the typewriter,and can just as easily be used for stencil duplicating. When the abovementioned papers are contacted with water, the binder material will bedissolved, thus releasing the individual fibres from the sheet andleaving a soft pulpy mass. This procedure takes only a few minutes. Buteven before the paper sheet has fully disintegrated, the writing on saidpaper becomes undecipherable immediately when subjecting it to theaction of hot or cold water. Not only single sheets of paper, but evendocuments or books in which many sheets of this type are superimposedmay be made undecipherable in this way.

The novel paper products are especially suitable for military purposes.So, radio operators no longer have to burn each sheet after receptionand decoding of a cable. It is enough to destroy the text written on thenovel paper products by dipping it into water.

The novel paper products are also suitable for the production of logbooks for battle ships and submarines. If such naval units should sinkin shallow enemy coastal water, it is impossible for enemy divers torescue and decipher the log books which may contain secret matter.

The invention will now be described with reference to the followingtypical examples in which the proportions given are by weight.

Example 1 A matted fibre fleece composed of 100% staple fibres with aweight of 24 grams per square metre is impregnated with an aqueousmixture containing:

30 parts of cellulose glycolate, 20 parts of maize dextrine,

15 parts of chalk,

15 parts of kaolin,

40 parts of gypsum,

1 part of wetting agent.

The intermediate product obtained after impregnating on a screensaturator and drying, with a Weight of about 80 grams per square metre,is smoothed, after wetting to a moisture content of about 5%, on aheated calender at about C., and cut. A smooth, strong writing paper isobtained, which swells on cold water in a few minutes and, afterdissolution of the fibre bond, leaves behind a mixture of insolublefibres.

Example 2 A carded fleece of 50% staple fibres and 50% polyamide fibres,with a weight of 60 grams per square metre, is impregnated with anaqueous mixture containing:

50 parts of polyacrylate, 10 parts of urea,

20 parts of gypsum,

10 parts of pearl white, 10 parts of talcum,

1 part of Wetting agent.

After impregnation and drying an intermediate product with a weight of150 grams per square metre is obtained,

which is wetted and calendered with increasing pressure at about 150 C.,and thereupon cut. If the resulting paper is soaked in water, it breaksup into its fibrous constituents.

Example 3 A longitudinally directed carded fleece, consisting of 25%polyamide fibres, 25% acetate staple fibres, 20% ramie, 30% cotton, witha weight of 16 grams per square metre, is impregnated with an aqueousmixture containmg:

33 parts of water-soluble starch, 5 parts of polyglycol,

15 parts of microcellulose,

20 parts of titanium dioxide,

20 parts of gypsum,

6 parts of lithopone,

1 part of wetting agent.

The impregnated and dried first stuff with a weight of about 40 gramsper square metre is calendered, after wetting, with a roll temperatureof about 100 C. This thinner paper disintegrates into its constituentsafter a very short time in water.

I claim:

1. In a method of producing a writing paper which in Water disintegratesinto its individual components, the steps of impregnating a fleece ofcardable textile fibres with an aqueous dispersion containing awater-insoluble filler material and a Water-soluble film-forming binderin such amounts as to incorporate said binder material in an amount ofto 200 percent, based upon the weight of the dry fibre fleece, dryingthe thus resulting structure, re-wetting said dry structure to amoisture content of about 3 to 10 percent and smoothing it on a heatedcalender at a temperature between and C.

2. A writing paper which in water disintegrates into its individualcomponents consisting of cardable textile fibres being bonded togetherwith a Water-soluble filmforming binder and containing insoluble fillermaterial.

References Cited in the file of this patent UNITED STATES PATENTS1,518,944 Sulzberger Dec. 9, 1924 2,208,653 Whitehead July 23, 19402,402,542 Foote et al June 25, 1946 2,705,688 Ness et al Apr. 5, 19552,880,113 Drelich Mar. 31, 1959 2,893,754 Richter et al. July 7, 1959

1. IN A METHOD OF PRODUCING A WRITING PAPER WHICH IN WATER DISINTEGRATESINTO ITS INDIVIDUAL COMPONENTS, THE STEPS OF IMPREGNATING A FLEECE OFCARDABLE TEXTILE FIBRES WITH AN AQUEOUS DISPERSION COTAINING AWATER-INSOLUBLE FILLER MATERIAL AND A WATER-SOLUBLE FILM-FORMING BINDERIN SUCH AMOUNTS AS TO INCORPORATE SAID BINDER MATERIAL IN AN AMOUNT OF40 TO 200 PERCENT, BASED UPON THE WEIGHT OF THE DRY FIBRE FLEECE, DRYINGTHE THUS RESULTING STRUCTURE, RE-WETTING SAID DRY STRUCTURE TO AMOISTURE CONTENT OF ABOUT 3 TO 10 PERCENT AND SMOOTHING IT ON A HEATEDCALENDER AT A TEMPERATURE BETWEEN 50 AND 150*C.